ABSTRACT
Recent studies have identified a class of small non-coding RNA molecules, named microRNA (miRNA), that is dysregulated in malignant brain glioblastoma. Substantial data have indicated that miRNA-16 (miR-16) plays a significant role in tumors of various origins. This miRNA has been linked to various aspects of carcinogenesis, including cell apoptosis and migration. However, the molecular functions of miR-16 in gliomagenesis are largely unknown. We have shown that the expression of miR-16 in human brain glioma tissues was lower than in non-cancerous brain tissues, and that the expression of miR-16 decreased with increasing degrees of malignancy. Our data suggest that the expression of miR-16 and nuclear factor (NF)-κB1 was negatively correlated with glioma levels. MicroRNA-16 decreased glioma malignancy by downregulating NF-κB1 and MMP9, and led to suppressed invasiveness of human glioma cell lines SHG44, U87, and U373. Our results also indicated that upregulation of miR-16 promoted apoptosis by suppressing BCL2 expression. Finally, the upregulation of miR-16 in a nude mice model of human glioma resulted in significant suppression of glioma growth and invasiveness. Taken together, our experiments have validated the important role of miR-16 as a tumor suppressor gene in glioma growth and invasiveness, and revealed a novel mechanism of miR-16-mediated regulation in glioma growth and invasiveness through inhibition of BCL2 and the NF-κB1/MMP-9 signaling pathway. Therefore, our experiments suggest the possible future use of miR-16 as a therapeutic target in gliomas.
Subject(s)
Brain Neoplasms/metabolism , Cell Proliferation , Glioma/metabolism , MicroRNAs/physiology , Proto-Oncogene Proteins c-bcl-2/genetics , Signal Transduction , Animals , Apoptosis , Brain Neoplasms/genetics , Brain Neoplasms/pathology , Cell Line, Tumor , Female , Gene Expression Regulation, Neoplastic , Glioma/genetics , Glioma/pathology , Humans , Male , Matrix Metalloproteinase 9/metabolism , Mice , Mice, Nude , Middle Aged , NF-kappa B p50 Subunit/metabolism , Neoplasm Invasiveness , Neoplasm Transplantation , Proto-Oncogene Proteins c-bcl-2/metabolism , RNA Interference , Tumor BurdenABSTRACT
BACKGROUND: The gliomas represent the most common primary malignant brain tumors; however, little is known about the molecular pathogenesis of these tumors. Recent research reveals that the oncogenesis and development of gliomas have a close relation to the overexpression of several oncogenes and the inactivation of tumor suppressor genes. Whether the RING finger protein, RNF138, a newly discovered protein, plays a role in glioma oncogenesis is unknown. The present study investigates the expression levels of RNF138 mRNA in glioma samples and noncancerous brain samples and its function in the human glioma cell line U251. METHODS: RT-PCR was used to ascertain the expression of RNF138 mRNA in the glioma cell lines U251, SHG44, U87, A172, and U373. The RNF138 mRNA expression levels of 35 pathological confirmed glioma samples (Grade I - 4 cases, Grade II - 13 cases, Grade III - 11 cases, and Grade IV - 7 cases) and five noncancerous brain tissue samples were analyzed by real-time quantitative PCR. By RNA interference (RNAi) with the lentivirus vector system, the expression of RNF138 was inhibited in the human astrocytomas-glioblastoma multiforme cell line U251. The effects of RNF138-knockdown on cell proliferation were assessed by Cellomics, and cell cycle and cell apoptosis were assessed by FACS. RESULTS: The RNF138 mRNA is expressed in the five glioma cell lines, and its expression level is significantly higher in glioma tissue than in noncancerous brain tissue. By down-regulation of RNF138 expression, U251 cell proliferation was inhibited and cell apoptosis increased. At the same time, S stage cells lessened and G2 stage cells increased. CONCLUSION: The RNF138 gene is highly expressed in glioma tissue and glioma cell lines. It plays an important role in glioma cell proliferation, apoptosis, and cell cycle.
